1. Field of the Invention
The present invention relates to a fluxless soldering process using a silane-containing atmosphere.
2. Description of the Prior Art
U.S. Pat. No. 3,133,348 Cape discloses a method of welding or brazing where an inert gas such as argon is passed through liquid carbon tetrachloride to convert the liquid tetrachloride into a gas which is directed at a welding area in order to protect the welding operation against the action of air and to remove oxides from the surfaces being welded.
U.S. Pat. No. 3,665,590 Percival discloses a semiconductor flip-chip soldering method. A hot reducing gas is passed through a reducing gas guidance device onto surface oxidized solder which is upon the electrodes of the flip-chip to melt the surface oxidized solder and to purify the surface oxidized solder. Simultaneously, the hot reducing gas is also passed onto surface oxidized solder on bonding pads of the flip-chip package to melt and purify the same. Due to the purification of the surface oxidized solder, when the solder on the electrodes and on the bonding pads is brought together, the purified solder easily coalesces together. Illustrative hot reducing gases include hydrogen gas, hot cracked ammonia gas and any other gas which can reduce and melt the surface oxidized solder.
U.S. Pat. No. 3,681,132 Pammer et al discloses a method of producing a protective layer of SiO.sub.2 on the surface of a semiconductor wafer. A gas jet of SiH.sub.4 and an inert gas is passed over heated semiconductor wafers on a substrate and thickly coats the substrate in the area of the wafers, simultaneously causing oxygen to act on the wafers to provide a homogeneous layer of SiO.sub.2 on the wafers. Use of SiH.sub.4 in a solder environment is not disclosed. Illustrative inert gases include nitrogen, argon and other noble gases.
U.S. Pat. No. 3,705,457 Tardoskegyi discloses a wave soldering process for relatively flat work pieces such as printed circuit boards. The boards are pretinned and soldered using a technique where molten solder is forced upwardly through a nozzle to form a standing wave of molten solder which is gently curved in a direction parallel to the work travel direction. A flat work piece is moved in the work travel direction with its undersurface in contact with the standing wave and, as its forward end emerges from the wave, it defines, with the surface of the wave, a space. Inert gas under pressure is applied to this space to exclude air from the solder coated undersurface of the work piece to inhibit oxidation.
It is often conventional in the art of manufacturing semiconducting devices to reflow solder prior to actual joining of a semiconductor chip to a ceramic substrate. The purpose of such reflow is to insure that the solder has the desired shape to yield the desired bond.
It is further known that semiconductor chips can be soldered to appropriate contacts on a ceramic substrate using a chip joining technique where soldering (joining) is effected in a carrier or furnace gas without using a flux.
It is further known that soldering techniques as described above can be effected using a flux.
It is finally known that lead-tin solders are the most commonly used solders for joining semiconductor chips to ceramic substrates.